No abstract

Impedance spectra obtained by fast Fourier transformation of the response to a multi-sine potential perturbation are shown to be consistent with the Kramers–Kronig relations, even for systems that are nonlinear and nonstationary. These results, observed for measurements on a Li/SOCl2 battery, were confirmed by numerical simulations. Consistency with the Kramers–Kronig relations was confirmed by use of the measurement model developed by Agrawal et al. and by a linear measurement model approach developed by Boukamp and implemented by Gamry. The present work demonstrates that application of the Kramers–Kronig relations to the results of multi-sine measurements cannot be used to determine whether the experimental system satisfies the conditions of linearity, causality and stability.

The first thieno[3,4-b]pyrazine (TP) based non-fullerene acceptor was synthesized and named as TP21, which shows a narrow band gap of 1.65 eV and a high-lying LUMO of -3.61 eV. Organic solar cells based on J61:TP21 realized a moderate power conversion efficiency (PCE) of 5.81% with a high open-circuit voltage (Voc) of 1.05 V.